对carAB操纵子的分子研究表明，carB基因是柑橘黄龙病菌游动和生物膜形成所必需的。
Molecular study on the carAB operon reveals that carB gene is required for swimming and biofilm formation in Xanthomonas citri subsp. citri.
作者信息
Zhuo Tao, Rou Wei, Song Xue, Guo Jing, Fan Xiaojing, Kamau Gicharu Gibson, Zou Huasong
机构信息
College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.
Hebei Institute of Engineering Technology, Shijiazhuang, 050091, China.
出版信息
BMC Microbiol. 2015 Oct 23;15:225. doi: 10.1186/s12866-015-0555-9.
BACKGROUND
The carA and carB genes code the small and large subunits of carbamoyl-phosphate synthase (CPS) that responsible for arginine and pyrimidine production. The purpose of this work was to study the gene organization and expression pattern of carAB operon, and the biological functions of carA and carB genes in Xanthomonas citri subsp. citri.
METHODS
RT-PCR method was employed to identify the full length of carAB operon transcript in X. citri subsp. citri. The promoter of carAB operon was predicted and analyzed its activity by fusing a GUS reporter gene. The swimming motility was tested on 0.25% agar NY plates with 1% glucose. Biofilm was measured by cell adhesion to polyvinyl chloride 96-well plate.
RESULTS
The results indicated that carAB operon was composed of five gene members carA-orf-carB-greA-rpfE. A single promoter was predicted from the nucleotide sequence upstream of carAB operon, and its sensitivity to glutamic acid, uracil and arginine was confirmed by fusing a GUS reporter gene. Deletion mutagenesis of carB gene resulted in reduced abilities in swimming on soft solid media and in forming biofilm on polystyrene microtiter plates.
CONCLUSIONS
From these results, we concluded that carAB operon was involved in multiple biological processes in X. citri subsp. citri.
背景
carA和carB基因编码氨甲酰磷酸合成酶（CPS）的小亚基和大亚基，该酶负责精氨酸和嘧啶的产生。本研究旨在探究柑桔黄龙病菌中carAB操纵子的基因组织、表达模式以及carA和carB基因的生物学功能。
方法
采用RT-PCR方法鉴定柑桔黄龙病菌中carAB操纵子转录本的全长。通过融合GUS报告基因预测carAB操纵子的启动子并分析其活性。在含有1%葡萄糖的0.25%琼脂NY平板上检测游动性。通过细胞对聚氯乙烯96孔板的粘附来测定生物膜形成情况。
结果
结果表明，carAB操纵子由五个基因成员carA-orf-carB-greA-rpfE组成。从carAB操纵子上游的核苷酸序列预测到一个单一启动子，通过融合GUS报告基因证实了其对谷氨酸、尿嘧啶和精氨酸的敏感性。carB基因的缺失诱变导致在软固体培养基上的游动能力和在聚苯乙烯微量滴定板上形成生物膜的能力降低。
结论
从这些结果中，我们得出结论，carAB操纵子参与了柑桔黄龙病菌的多个生物学过程。
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